Shut-off valve control device, shut-off valve control system, method for calculating shut-off valve control coefficient, and method for controlling shut-off valve

ABSTRACT

Provided are: a shut-off valve control device which is capable of reducing the difference between a set opening amount and the actual opening amount, when executing a partial valve stroke test; a shut-off valve control system; a method for calculating a shut-off valve control coefficient; and a method for controlling a shut-off valve. This shut-off valve control device is provided with a microcomputer for controlling the opening and closing of a solenoid valve which supplies air from an air supply source, to a cylinder of an air cylinder for controlling a valve shaft of a shut-off valve, and discharges said air. The microcomputer acquires a set opening amount of the shut-off valve. Furthermore, the microcomputer controls the solenoid valve to a value obtained by dividing the acquired set opening amount by a predetermined coefficient C.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending application: “VALVE CONTROLDEVICE, VALVE CONTROL SYSTEM, VALVE CONTROL COEFFICIENT CALCULATIONMETHOD, AND VALVE CONTROL METHOD” filed even date herewith in the namesof Masayuki Kobayashi and Kazuomi Abe as a national phase entry ofPCT/JP2017/026263, which application is assigned to the assignee of thepresent application and is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a shut-off valve control device, ashut-off valve control system, a shut-off valve control coefficientcalculation method, and a shut-off valve control method.

BACKGROUND ART

A pipeline of oil, gas or the like in a plant facility is provided witha shut-off valve composed of a ball valve or the like in order to shutoff the line urgently when an abnormality occurs in the facility. As forthe shutoff valve, after installation in the plant facility, the fullstroke operation test (also referred to as full valve stroke test orfull stroke test) of the shutdown (full open to full close) wasconducted about once a year to confirm the presence or absence offailure.

However, closing the shut-off valve completely shuts down the plant andinterferes with the normal operation. Therefore, during the normaloperation, it was not possible to carry out an operation test of theshut-off valve. Therefore, by performing an operation test to operatethe shut-off valve from full opening to a predetermined opening degree(also referred to as partial valve stroke test or partial stroke test),it becomes possible to test the shut-off valve operation without fullyclosing the shut-off valve, that is, without stopping the plant (forexample, refer to Patent Literature 1).

PRIOR ART DOCUMENT Patent Literature

Patent Literature 1: JP 2009-92110 A

SUMMARY OF INVENTION Technical Problem

The shut-off valve control system described in Patent Literature 1includes a shut-off valve, an air cylinder drive valve that opens andcloses the shut-off valve, and an electromagnetic valve (solenoid valve)that supplies or exhausts air to a cylinder of the air cylinder drivevalve.

In the configuration described above, the shut-off valve is opened orclosed by operating the electromagnetic valve by an electric signal andoperating the cylinder by supplying or exhausting air into the cylinderby actuation of the electromagnetic valve.

Here, the electromagnetic valve is operated by an electric signal andhas a high reaction speed, but the shut-off valve is opened and closedby an air cylinder drive valve operated by air, and operates later thanthe electromagnetic valve, and the control of the shut-off valve tendsto be delayed with respect to the electric signal.

Therefore, when the partial valve stroke test (hereafter referred to asPVST) is performed, even if the opening and closing drive is performedto the opening degree set by the user, there is a problem that adeviation occurs between the set opening degree and the actual openingdegree of the shut-off valve.

Accordingly, an object of the present invention is to provide a shut-offvalve control device, a shut-off valve control system, a shut-off valvecontrol coefficient calculation method, and a shut-off valve controlmethod which can make small the difference of the set opening degree andthe actual opening degree, when performing PVST.

Solution to Problem

According to one aspect of the present invention, there is provided ashut-off valve control device provided with control means forcontrolling an electromagnetic valve that supplies and exhausts air froman air supply source to a cylinder of an air cylinder that controls avalve shaft of a shut-off valve, including:

set opening degree acquisition means for acquiring a set opening degreeof the shut-off valve; and

opening degree detecting means for detecting an opening degree of theshut-off valve,

wherein the control means operates the electromagnetic valve until theopening degree detected by the opening degree detection means becomes avalue obtained by dividing the set opening degree by a predeterminedcoefficient.

Further, according to a second aspect of the invention, there isprovided the shut-off valve control device as described in the firstaspect,

wherein the coefficient is calculated based on a deviation between anactual opening degree of the shut-off valve and the set opening degree.

Further, according to a third aspect of the present invention, there isprovided a shut-off valve control system provided with a shut-off valve,an air cylinder for controlling rotation of a valve shaft of theshut-off valve, and an electromagnetic valve for supplying andexhausting air from an air supply source to a cylinder of the aircylinder, including:

a shut-off valve control device as described in the first or secondaspect.

Further, according to a fourth aspect of the present invention, there isprovided the shut-off valve control system as described in the thirdaspect,

wherein adjustment means for adjusting a flow rate of the air isprovided between the electromagnetic valve and the air cylinder.

Further, according to a fifth aspect of the present invention, there isprovided a shut-off valve control coefficient calculation method ofcalculating a coefficient by controlling means for controlling anelectromagnetic valve that supplies and exhausts air from an air supplysource to a cylinder of an air cylinder that controls a valve shaft ofthe shut-off valve, including the steps of:

a preliminary operation step for operating the shut-off valve to apredetermined set opening degree;

an actual opening degree detection step for detecting an actual openingdegree of the shut-off valve in the preliminary operation step;

a deviation calculation step for calculating a deviation of the setopening degree and the actual opening degree; and

a coefficient calculation step for calculating the coefficient based onthe deviation calculated in the deviation calculation step.

Further, according to a sixth aspect of the present invention, there isprovided the shut-off valve control coefficient calculation method asdescribed in the fifth aspect,

wherein the preliminary operation step is performed for each of theplurality of set opening degrees.

Further, according to a seventh aspect of the present invention, thereis provided the shut-off valve control coefficient calculation method asdescribed in the fifth or sixth aspect,

wherein the preliminary operation step operates the shut-off valve tothe set opening degrees a plurality of times per one set opening degree.

Further, according to an eighth aspect of the present invention, thereis provided a shut-off valve control method of a shut-off valve controldevice provided with a control device for controlling an electromagneticvalve for supplying and exhausting air from an air supply source to acylinder of an air cylinder for controlling a valve shaft of a shut-offvalve, including the steps of:

a set opening degree acquisition step for acquiring a set opening degreeof the shut-off valve;

an opening degree detection step for detecting an opening degree of theshut-off valve; and

a control step for operating the electromagnetic valve until the openingdegree detected in the opening degree detection step becomes a valueobtained by dividing the set opening degree by a predeterminedcoefficient.

Effect of the Invention

According to the first aspect described above, the control meanscontrols the opening of the electromagnetic valve to a value obtained bydividing the set opening degree by a predetermined coefficient. Thus,the set opening degree can be changed inside the control means to avalue in consideration of the delay of the operation of the shut-offvalve by the coefficient. Therefore, the actual opening degree can becontrolled to be a value close to the set opening degree, and thedeviation between the set opening degree and the actual opening degreecan be reduced. In addition, since it can be realized only by electricalcontrol, there is no need for a mechanical mechanism such as extendingthe needle under a predetermined condition to apply a brake, and theneed for additional components for testing is not required.

According to the second aspect, since the coefficient is calculatedbased on the deviation of the actual opening degree of the shut-offvalve and the set opening degree, the coefficient can be calculated notfrom a simple difference but from variations based on a plurality ofdata, and the coefficients can be made more accurate.

According to the third aspect, in the shut-off valve control systemincluding a shut-off valve, an air cylinder for controlling rotation ofa valve shaft of the shut-off valve, and an electromagnetic valve forsupplying and exhausting air from an air supply source to the cylinderof the air cylinder, the deviation between the set opening degree andthe actual opening degree can be reduced.

According to the fourth aspect, since the adjustment means for adjustingthe flow rate of air is provided between the electromagnetic valve andthe air cylinder, the exhausting amount is controlled by throttling theamount of air discharged from the air cylinder by the adjustment means.Therefore, the operating speed of the cylinder is limited, which makesit easy to control the opening degree of the shut-off valve. Therefore,the deviation between the set opening degree and the actual openingdegree can be reduced.

According to the fifth aspect, first, the preliminary operation step ofoperating the shut-off valve to a predetermined set opening degree isperformed, the actual opening degree of the shut-off valve in thepreliminary operation step is detected, and the deviation between theset opening degree and the actual opening degree is calculated, and thecoefficient based on the deviation is calculated. Thus, the coefficientcan be calculated based on the deviation of the actual opening degree ofthe shut-off valve and the set opening degree, the coefficient can becalculated from the variation based on a plurality of data, and thecoefficient can be calculated accurately. Then, by means of thiscoefficient, it is possible to change the set opening degree to a valuetaking into account the delay of the operation of the shut-off valveinside the control means. Therefore, the actual opening degree can becontrolled to a value close to the set opening degree, and the deviationbetween the set opening degree and the actual opening degree can bereduced.

According to the sixth aspect, since the preliminary operation step isperformed for each of the plurality of set opening degrees, the accuracyof the coefficient can be further improved.

According to the seventh aspect, since the preliminary operation stepoperates the shut-off valve to the set opening degree a plurality oftimes per one set opening degree. Therefore, more data for calculatingthe coefficient can be obtained, and the accuracy of the coefficient canbe further improved.

According to the eighth aspect, in the control step, the electromagneticvalve is controlled to open to a value obtained by dividing the setopening degree by a predetermined coefficient. Thus, By means of thecoefficient, the set opening degree can be changed inside the controlmeans to a value taking into account the delay of the operation of theshut-off valve. Therefore, the actual opening degree can be controlledto be a value close to the set opening degree, and the deviation betweenthe set opening degree and the actual opening degree can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a shut-off valve control system having ashut-off valve control device according to a first embodiment of thepresent invention;

FIG. 2 is a partial cross-sectional view of the shut-off valve controlsystem shown in FIG. 1;

FIG. 3 is an explanatory drawing showing the structures of a solenoidvalve and an air cylinder shown in FIG. 1;

FIG. 4 is a block diagram showing a functional structure of the shut-offvalve control device shown in FIG. 1;

FIG. 5 is a flowchart of an operation at the time of a setting operationtest (PVST) including prediction of a failure of the shut-off valvecontrol device shown in FIG. 1;

FIG. 6 is an explanatory view explaining a problem in conventional PVST;

FIG. 7 is an explanatory view explaining an operation principle of ashut-off valve control device according to the first embodiment of thepresent invention;

FIG. 8 is a flowchart of coefficient calculation operation of theshut-off valve control device shown in FIG. 1;

FIG. 9 is a table of an example comparing a setting opening degree andan actual opening degree in the case with a coefficient, and a casewithout a coefficient;

FIG. 10 is a flowchart of an operation at the time of a settingoperation test (PVST) including prediction of a failure of the shut-offvalve control device according to a second embodiment of the presentinvention;

FIG. 11 is an explanatory view explaining an operation principle of ashut-off valve control device according to the second embodiment of thepresent invention;

FIG. 12 is an explanatory view explaining an operation principle of ashut-off valve control device according to a third embodiment of thepresent invention;

FIG. 13 is a flowchart of a time difference calculation operation of theshut-off valve control device according to the third embodiment of thepresent invention;

FIG. 14 is an explanatory drawing showing the structures of a solenoidvalve and an air cylinder of a shut-off valve control system accordingto a fourth embodiment of the present invention;

FIG. 15 is a cross-sectional view of a configuration of a speedcontroller shown in FIG. 14;

FIG. 16 is an operation explanatory drawing of the speed controllershown in FIG. 14; and

FIG. 17 is a flowchart of an operation at the time of a settingoperation test (PVST) including prediction of a failure of the shut-offvalve control device according to the fourth embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS First Embodiment

Hereinafter, a first embodiment of the present invention will bedescribed with reference to drawings.

FIGS. 1 and 2 show the configuration of a shut-off valve control systemaccording to a first embodiment of the present invention, FIG. 1 is afront view, and FIG. 2 is a partial cross-sectional view. The shut-offvalve control system includes a shut-off valve 1, an air cylinder 3attached to the top of the shut-off valve 1 via a fixed yoke 2 andcontrolling the opening degree of the shut-off valve 1, and an outdoortype or an explosion-proof construction type position box 4 mounted onthe top of the air cylinder 3. The position box 4 accommodates alater-described solenoid valve 5, a pressure sensor (electronic digitalpressure gauge) 6, a microcontroller (hereinafter referred to as amicrocomputer) 7, an opening degree sensor 8, a solenoid valve controlpower source 10, and the like.

The shutoff valve 1 is, for example, a ball valve having a ball-likevalve body 1 a, and is connected to a pipeline of a plant facility orthe like. An upwardly extending valve stem 1 b is connected to the valvebody 1 a. The valve body 1 a is switched between a fully open state (seeFIG. 2) and a fully closed state (not shown) when the valve shaft 1 b isrotated 90 degrees. A periphery of the valve body 1 a is sealed by asheet packing 1 c, and a periphery of the valve shaft 1 b is sealed by agland packing 1 d.

As shown in FIG. 3, the air cylinder 3 is provided with a pair ofpistons 33 and 34 connected by a piston rod 32 in a single-actingpneumatic cylinder 31. One piston 33 is urged to slide in a valveclosing direction (the right direction in FIG. 3) by the urging force ofa coil spring 35 disposed in one end of the cylinder 31. The otherpiston 34 is urged to slide toward an valve-opening direction (the leftdirection in FIG. 2) against the biasing force of the coil spring 35 bythe air supplied from an outlet port OUT of the solenoid valve 5connected to an air inlet 36 provided at the other end of the cylinder31. The piston rod 32 is provided with a transmission mechanism 37 thatconverts a reciprocating motion of the piston rod 32 into a rotationalmotion and transmits the rotational motion to the valve shaft 1 b. Thetransmission mechanism 37 has an engagement pin 37 a protruding from thepiston rod 32, and a bifurcated engagement piece 37 b attached to anupper end of the valve shaft 1 b. A tip of the bifurcated engagementpiece 37 b is engaged with the engagement pin 37 a, and the bifurcatedengagement piece 37 b is rotated by the lateral movement of theengagement pin 37 a, whereby the valve shaft 1 b is rotated 90 degrees.Incidentally, the air cylinder 3 is not limited to a single-actingcylinder as illustrated, but may be another type such as a double-actingcylinder.

The solenoid valve 5 as an electromagnetic valve incorporates twothree-way solenoid valves, a large flow three-way solenoid valve 5A anda small flow three-way solenoid valve 5B, in one body. The large flowthree-way solenoid valve 5A has solenoids A and B for valve switching,has a large effective cross-sectional area of the valve, and rapidlydrives the air cylinder 3 in a valve closing direction to shut off theshut-off valve 1 urgently when an abnormality occurs in the pipeline.The small flow three-way solenoid valve 5B has solenoids C and D forswitching the valve, and the effective cross-sectional area of the valveis smaller than the large flow three-way solenoid valve 5A, and is foroperation test used in an operation test of the system. An inlet portIN, an outlet port OUT and an exhaust port EXH of each of the large flowthree-way solenoid valve 5A and the small flow three-way solenoid valve5B are respectively connected to each other, and are respectively commonones provided in the body. The solenoid valve 5 is connected to the airfrom the air supply source 11 located outside the position box 4 andsupplies the air from the common inlet port IN via the large flowthree-way solenoid valve 5A or the small flow three-way solenoid valve5B to the cylinder 31 of the air cylinder 3, and exhausts the air in thecylinder 31 to the atmosphere from the common outlet port OUT via thecommon exhaust port EXH via the large flow three-way solenoid valve 5Aor the small flow three-way solenoid valve 5B.

Incidentally, in the present embodiment, although the solenoid valve 5is described as having the two-system three-way valve as describedabove, the solenoid valve 5 may has one-system. That is, one-system ofthree-way valve may be used for both emergency shut-off and operationtest. Also, the solenoid valve 5 is not limited to the illustratedthree-way solenoid valve of the all-port block three-position doublesolenoid but may be another type such as a two-position three-waysolenoid valve.

FIG. 4 is a block diagram showing an electrical configuration of theshut-off valve control device according to the present embodiment. Theshut-off valve control device 100 includes a solenoid valve 5, apressure sensor 6, a microcomputer 7, an opening degree sensor 8, aninternal power supply 12, a communication circuit 13, a loop currentcontroller 14, a reverse voltage protection circuit 15, a valve testswitch 16, a current/resistance measuring circuit 17, and an A/Dconverter 18.

The pressure sensor 6 includes an IN-side pressure sensor 6A and anOUT-side pressure sensor 6B. The IN-side pressure sensor 6A measures thepressure supplied from the air supply source 11 to the solenoid valve 5.The OUT side pressure sensor 6B measures the pressure on the OUT side ofthe solenoid valve 5 and the internal pressure of the cylinder 31.

The microcomputer 7 includes a central processing unit (CPU), a memorysuch as a read only memory (ROM) and a random access memory (RAM), andcontrols the entire operation of the shut-off valve control device 100with a program executed by the CPU. The microcomputer 7 performs, forexample, control of the solenoid valve 5 at the time of PVST describedabove, calculation operation of a coefficient to be used at the time ofPVST, and the like. That is, the microcomputer 7 functions as controlmeans for controlling the opening and closing of the solenoid valve 5(electromagnetic valve).

The opening degree sensor 8 as opening degree detection means iscomposed, for example of a potentiometer etc., and detects the actualopening degree of the shut-off valve 1 by measuring an angle of thevalve shaft 1 b.

The internal power supply 12 is a power supply for driving the shut-offvalve control device 100. The communication circuit 13 performs datatransmission/reception with external input/output and the microcomputer7. The loop current controller 14 performs predetermined output currentcontrol under the control of the microcomputer 7.

The reverse voltage protection circuit 15 protects an internal circuitsuch as the microcomputer 7 from a reverse voltage generated when asolenoid valve control power supply 10 is reversely connected. The valvetest switch 16 is a switch for performing the PVST and a full valvestroke test (hereinafter referred to as FVST) of the shut-off valveusing the solenoid valve 5. The current/resistance measuring circuit 17measures the current when the solenoid valve 5 is energized, andmeasures the resistance when the solenoid valve 5 is not energized. TheA/D converter 18 converts analog signals of the measurement result ofthe current/resistance measuring circuit 17 and the measurement resultof the opening degree sensor 8 into digital signals.

Next, a normal operation of the shut-off valve control system will bedescribed. First, the solenoid valve 5 for switching the air cylinder 3has two valves (the large flow three-way solenoid valve 5A and the smallflow three-way solenoid valve 5B) which are three-way valves in onebody. Therefore, the large flow three-way solenoid valve 5A is usuallyused. At this time, the small flow three-way solenoid valve 5B iscontrolled to be in a power stop state, and is in the all-port blockstate in which all three ports are closed. The large flow three-waysolenoid valve 5A and the small flow three-way solenoid valve 5B areelectrically interlocked by the control of the microcomputer 7 so thatwhen one solenoid valve is energized, the other solenoid valve is in thepower stop state. Therefore, both will not be energized at the sametime.

When the solenoid A of the large flow three-way solenoid valve 5A is inthe power stop state and power is supplied to the solenoid B, the airfrom the air supply source 11 flows from the common inlet port IN of thesolenoid valve 5 through the large flow three-way solenoid valve 5A andis supplied to the cylinder 31 from the inlet 36 via the common outletport OUT. Then, the piston 34 slides in the left direction, and theshut-off valve 1 is fully opened. As a result, while the solenoid B isenergized, operation of the pipeline is enabled. Incidentally, the largeflow three-way solenoid valve 5A is electrically interlocked by thecontrol of the microcomputer 7 so that the other solenoid is notenergized while one solenoid is energized.

Next, when the microcomputer 7 energizes the solenoid A based on anabnormality detection signal of the plant facility or an operationsignal of an emergency shut-off switch (not shown), the air in thecylinder 31 is exhausted from the common exhaust port EXH to theatmosphere from the outlet port OUT of the solenoid valve 5 via thelarge flow rate three-way solenoid valve 5A. Then, the piston 34 slidesfrom left to right due to the spring load, the valve shaft 1 b rotates90 degrees, and the shut-off valve 1 is fully closed. As a result, whilethe solenoid A is energized, the pipeline is shut off urgently.

In the above operation, either solenoid A or B is controlled to beenergized at all times, but as another operation example, if thesolenoid A remains in the power stop state and the solenoid B isenergized to make the shut-off valve in the fully opened state, and thenthe solenoid B also becomes in the power stop state, the large flowthree-way solenoid valve 5A is in the all port block state, and theshut-off valve 1 maintains in the fully opened state. Further, if thesolenoid B remains in the power stop state and the solenoid A isenergized to make the shut-off valve in the fully closed state, and thenthe solenoid A is also in the power stop state, the large flow three-waysolenoid valve 5A is in the all port block state, and the shut-off valve1 maintains in the fully closed state. In this manner, power consumptioncan be reduced by controlling both solenoids A and B in the power stopstate after the shut-off valve is in the fully opened state or in thefully closed state.

Next, an operation at the time of setting operation test (PVST)including prediction of a failure will be described with reference to aflowchart of FIG. 5. At the time of operation test, the small flowthree-way solenoid valve 5B is used. Although FIG. 5 is described asPVST, it can also be applied to FVST by fully closing the set openingdegree. Incidentally, this flowchart is executed by the microcomputer 7.

First, the set opening degree of the shut-off valve 1 is set (stepS100). The set opening degree is acquired by the microcomputer 7 via thecommunication circuit 13 and the like, and is set in the microcomputer7. That is, the microcomputer 7 functions as set opening degreeacquisition means that acquires the set opening degree of the shut-offvalve 1. Then, for example, the valve test switch 16 is operated, andthe following operation is performed.

Next, the detection value of the OUT side pressure sensor 6B is acquiredand checked (step S101). If the shut-off valve 1 is fully closed (stepS102: the shut-off valve 1 is fully closed), the test result is held inthe memory in the microcomputer 7 (step S117) to complete the test.Since the OUT side pressure sensor 6B can measure the internal pressureof the cylinder 31, by setting the position of the piston 34 when theshut-off valve 1 is fully closed, the position of the piston 34 when theshut-off valve 1 is fully opened, and the internal pressure value of thecylinder 31 in each case in the microcomputer 7 preliminary, whether theshut-off valve 1 is fully closed or fully opened can be determined.

On the other hand, if the shut-off valve 1 is fully opened (step S102:the shutoff valve 1 is fully opened), the shut-off valve 1 is closed(step S103). Specifically, the microcomputer 7 energizes the solenoid Cof the small flow three-way solenoid valve 5B, and the air in thecylinder 31 is exhausted from the common exhaust port EXH to theatmosphere from the outlet port OUT of the solenoid valve 5 via thesmall flow rate three-way solenoid valve 5B. Then, the piston 34 slidesfrom left to right due to the spring load.

Next, the allowable time until the set opening degree is reached is readfrom the internal memory or the like (step S104). The current detectionvalue of the OUT side pressure sensor 6B and the detection value of theopening degree sensor 8 are held in the internal memory or the like(step S105). The allowable time until reaching the set opening degree iscompared (checked) with the elapsed time from the start of closing theshut-off valve in step S103 to the present time (step S106).Incidentally, the allowable time is set preliminary in the microcomputer7. Further, the elapsed time may be measured by a timer or the likebuilt in the microcomputer 7.

If the result of comparison in step S106 indicates that the allowabletime is exceeded (step S107: exceeding the allowable time), the testresult is held in the memory in the microcomputer 7 (step S117) tocomplete the test. On the other hand, if the result of the comparison instep S106 does not exceed the allowable time (step S107: not exceedingthe allowable time), whether the set opening degree has been reached ischecked (step S108). As a result of comparison in step S106, if theallowable time is exceeded, it is determined that an abnormality such assticking of the shut-off valve 1 is found as a result of the test, andthe result is held.

Next, as a result of checking the set opening degree in step S108, ifthe set opening degree has not been reached (step S109: the settingopening degree has not been reached), the process returns to step S105,and step S105 and subsequent steps are executed again. On the otherhand, if the set opening degree is reached as a result of checking theset opening degree in step S108 (step S109: reached the set openingdegree), the shut-off valve 1 is opened (step S110).

When step S110 is executed, the microcomputer 7 makes the solenoid Cinto the power stop state, and makes the solenoid D energized. Then, theair from the air supply source 11 is supplied from the common inlet portIN of the solenoid valve 5 via the small flow rate three-way solenoidvalve 5B to the cylinder 31 from the inlet 36 via the common outlet portOUT. Then, the piston 34 slides in the left direction, and the shut-offvalve 1 goes to the fully opened state.

Next, the allowable time from the preliminary set opening degree to thefully opened state is read from the internal memory or the like (stepS111). The current detection value of the OUT side pressure sensor 6Band the detection value of the opening degree sensor 8 are held in theinternal memory or the like (step S112). The allowable time to the fullyopened state is compared (checked) with the elapsed time from the startof opening the shut-off valve 1 in step S110 to the present time (stepS113).

As a result of comparison in step S113, if the allowable time isexceeded (step S114: exceeding the allowable time), the test result isheld in the memory in the microcomputer 7 (step S117) and the test iscompleted. On the other hand, as a result of comparison in step S113, ifthe allowable time is not exceeded (step S114: not exceeding theallowable time), whether the shut-off valve 1 is fully opened again ischecked (step S115). As a result of comparison in step S113, if theallowable time is exceeded, it is determined that some abnormality isfound when returning from the set opening degree to the fully openedstate, and the result is held.

Next, as a result of checking whether the shut-off valve is fully openedin step S115, if not fully opened (step S116: not fully opened), theprocess returns to step S112, and step S112 and subsequent steps areexecuted again. On the other hand, as a result of checking whether theshut-off valve is fully opened in step S115, if fully opened (step S116:fully opened), the test result is held in the memory in themicrocomputer 7 (step S117) to complete the test. That is, when thesteps S114, S115, S116, and S117 are performed in order, it can bedetermined that the test has ended normally.

In the above-mentioned test (PVST), the solenoid valve 5 is operated byan electrical signal and the reaction speed is fast. However, since theshutoff valve 1 is opened and closed by the air cylinder 3 operated byair, the shut-off valve 1 is operated later than the solenoid valve 5.As a result, the control of the shut-off valve 1 tends to be delayedwith respect to the electrical signal. Therefore, even if the shut-offvalve 1 is driven to close to the opening degree (set opening degree)set by the user from the fully opened state during PVST, the shut-offvalve 1 stops (or shifts to open control) later than the solenoid valve5 stops (or shifts to open control) at the time of detection of the setopening degree. Therefore, the shut-off valve 1 is closed more than theset opening degree, and a deviation occurs between the set openingdegree and the actual opening degree of the shut-off valve 1 (see FIG.6).

Therefore, in the present embodiment, the microcomputer 7 performs anoperation based on a predetermined coefficient on the set opening degreeset by the user, and changes the set opening degree to a value largerthan the original value. Thus, the shut-off valve 1 is apparentlystopped before the set opening degree, and the actual opening degreeapproaches the value set by the user (see FIG. 7). FIG. 8 shows aflowchart of the above-described operation of calculating thepredetermined coefficient (a method of calculating the shut-off valvecontrol coefficient).

First, as an initial setting, the solenoid valve 5 is operated to causethe microcomputer 7 to recognize the detection values of the openingdegree sensor 8 when the shut-off valve 1 is fully opened and fullyclosed (step S201). Next, PVST is executed by the operation shown inFIG. 5 (step S202). This PVST is executed in the conventional mannerwithout using coefficients yet. Further, it is preferable to executePVST a plurality of times by changing the set opening degrees.Furthermore, it is preferable to execute PVST multiple times per one setopening degree.

Next, the actual opening degree of the shut-off valve 1 in the PVSTexecuted in step S202 is acquired for each set opening degree (stepS203). Next, the deviation α between each set opening degree and theactual opening degree is determined (step S204), and the average of thedeviation (standard deviation) β is determined (step S205). Then, thecoefficient C is calculated as C=1−β from the standard deviation βobtained in step S205 (step S206). That is, the coefficient C iscalculated based on the deviation of the actual opening degree of theshut-off valve 1 and the set opening degree.

According to the flowchart of FIG. 7, step S202 is a preliminaryoperation step, step S203 is an actual opening degree detection step,steps S204 and S205 are deviation calculation steps, and step S206 is acoefficient calculation step.

FIG. 9 shows the table which compared the examples of the set openingdegree (Setting Position) and the actual opening degree (ActualPosition) at the time of performing PVST by the case with a coefficientand the case without a coefficient. In the case of FIG. 9, PVST wasexecuted five times for each of three set opening degrees of 25%, 50%,and 75%, with and without the coefficient.

In FIG. 9, the coefficient is calculated based on data in the casewithout the coefficient as described above. In FIG. 9, the average (Ave)of the actual opening degree is calculated for each of the set openingdegree 25%, 50%, and 75%, and the deviation α between the average andthe set opening degree is calculated. Then, the standard deviation β iscalculated by adding the deviation α calculated for each of the setopening degree 25%, 50%, and 75%, and the coefficient C is calculated by1−β.

The coefficient C calculated in FIG. 9 is 0.817308. In the case of 25%,the set opening degree divided by the coefficient C is 30.588224, whichis a value larger than the set opening degree. Similarly, in the case ofthe setting opening degree 50%, it becomes 61.176446, and in the case ofthe setting opening degree 75% it becomes 91.764671, which are valueslarger than the setting opening degree. When the setting opening degreebecomes a large value, it is in front of the setting opening degreebecause control is performed from the fully opened state (100%) to theclosing direction when executing PVST.

If PVST is performed using a value instead of the set opening degreeobtained in this way, as shown in the row with the coefficient in FIG.9, the actual opening degree becomes a value close to the set openingdegree with any set opening degree, and it became clear that the errorwith coefficient was smaller than the error without coefficient.

The coefficient C calculated by the flowchart of FIG. 8 reads theallowable time until the opening degree based on the value of thedivision result by the coefficient C is reached instead of the setopening degree in step S104 of FIG. 5. Steps S106, S108, etc. are alsodetermined using the opening degree based on the division result insteadof the set opening degree. That is, the microcomputer 7 energizes thesolenoid C of the small flow three-way solenoid valve 5B of the solenoidvalve 5 (electromagnetic valve), and air in the cylinder 31 exhausts (tooperate) from the outlet port OUT of the solenoid valve 5 via the smallflow three-way solenoid valve 5B and from the common exhaust port EXHuntil the opening degree detected by the opening degree sensor 8(opening degree detection means) becomes a value obtained by dividingthe acquired set opening degree by a predetermined coefficient C.

Therefore, step S100 functions as a set opening degree acquisitionprocess, step S105 functions as an opening degree detection process, andsteps S108 and S109 function as a control process.

According to the present embodiment, the shut-off valve control device100 is provided with the microcomputer 7 that controls the opening andclosing of the solenoid valve 5 that supplies and exhausts air from theair supply source 11 to the cylinder 31 of the air cylinder 3 thatcontrols a valve shaft 1 b of the shut-off valve 1. The microcomputer 7acquires the set opening degree of the shut-off valve 1. Then, themicrocomputer 7 operates the solenoid valve 5 to a value obtained bydividing the acquired set opening degree by a predetermined coefficientC. Thus, the set opening degree can be changed by the coefficient Cinside the microcomputer 7 to a value in consideration of the delay ofthe operation of the shut-off valve 1. Therefore, the actual openingdegree can be controlled to a value close to the set opening degree, andthe deviation between the set opening degree and the actual openingdegree can be reduced. In addition, since it can be realized only byelectrical control, there is no need for a mechanical mechanism such asextending the needle under a predetermined condition to apply a brake,and the need for additional components for testing is not required.

Further, since the coefficient C is calculated based on the deviation ofthe actual opening degree of the shut-off valve 1 and the set openingdegree, the coefficient can be calculated not from a simple differencebut from variations based on a plurality of data, and the coefficientscan be made more accurate.

Second Embodiment

Next, a shut-off valve control system according to a second embodimentof the present invention will be described with reference to FIGS. 10and 11. Incidentally, the same components as those of the firstembodiment described above are denoted by the same reference signs andthe description thereof will be omitted.

In the present embodiment, the configuration of the shut-off valvecontrol system is the same as that shown in FIGS. 1 to 4. In the presentembodiment, the operation of the shut-off valve control system isdifferent. The operation at the time of operation test (PVST) at thetime of setting including prediction of failure in the presentembodiment will be described with reference to the flowchart of FIG. 10.

In the flowchart of FIG. 10, steps S300 to S304 are the same as stepsS100 to S104 of the flowchart of FIG. 5. In step S305, which is advancedfrom step S304, the detected value (actual opening degree) of theopening degree sensor 8 is held in an internal memory or the like, andwhether the detected value has reached a predetermined opening degree ischecked (step S306).

The predetermined opening degree is, for example, a value of about 120%of the set opening degree. If the predetermined opening degree is toolarge, the number of times to turn on the shut-off valve for a shorttime, which will be described later, increases, and the test timebecomes longer. On the other hand, if the predetermined opening degreeis too close to the set opening degree, as described in the TechnicalProblem, the set opening degree may be exceeded by delay of theoperation of the shut-off valve 1. So, in the present embodiment, it isdesirable that the predetermined opening degree is at least 150% of theset opening degree, namely, more than half of the movement amount fromthe fully opened state of the shut-off valve 1 to the set openingdegree. That is, the microcomputer 7 causes in the first operation theshut-off valve 1 to be closed more frequently than the second andsubsequent operations among opening and closing the solenoid valve 5(electromagnetic valve) a plurality of times.

As a result of step S306, when the predetermined opening degree has notbeen reached (step S307: the predetermined opening has not beenreached), the process returns to step S305, and the loop of steps S305to S307 is repeated until the predetermined opening degree is reached.

On the other hand, when the predetermined opening degree is reached as aresult of step S306 (step S307: the predetermined opening degree isreached), the shut-off valve 1 is stopped (step S308). Specifically, themicrocomputer 7 causes the solenoid C of the small flow rate three-waysolenoid valve 5B de-energized, and all the three ports are closed in anall-port block state. Then, both the supply and discharge of air arestopped, so the cylinder 31 and the shut-off valve 1 are delayed andstopped.

Next, the solenoid valve 5 is turned on for a short time (step S309),the detection value (actual opening degree) of the opening sensor 8 isheld in the internal memory or the like (step S310), and whether thedetected value has reached the set opening degree is checked (stepS311). Turning on the solenoid valve 5 means that the microcomputer 7energizes the solenoid C of the small flow three-way solenoid valve 5B.In this way, the air in the cylinder 31 is exhausted from the outletport OUT of the solenoid valve 5 to the atmosphere from the commonexhaust port EXH via the small flow rate three-way solenoid valve 5B,and the spring load causes the piston 34 to slide from left to right.Further, the short time is a time in which the opening degree of theshut-off valve 1 is closed by a small amount (about several %). That is,in step S309, the shut-off valve 1 is finely operated by turning on thesolenoid valve 5 for a short time.

The set opening degree checked in step S311 is not necessarily limitedto the same value as the set opening degree, and may be in apredetermined range (for example, ±several %) centered on the setopening degree.

As a result of step S311, when the opening degree has not reached (stepS312: the opening degree has not reached), the process returns to stepS309, and the solenoid valve 5 is turned on for a short time again.

On the other hand, when the set opening degree is reached as a result ofstep S311 (step S312: reached the setting opening degree), the allowabletime until reaching the set opening degree is compared (checked) withthe elapsed time from the start of closing the shut-off valve in stepS303 to the present time (step S313). Note that the allowable time ofthis embodiment is a time different from that of the first embodiment,and is a time taking into consideration that the predetermined openingdegree of step S306 and step S309 have been performed a plurality oftimes.

That is, in the present embodiment, the solenoid valve 5 is operated aplurality of times such that the opening degree of the shut-off valveapproaches the set opening degree (see FIG. 11). Although the number oftimes is n in FIG. 11, the number of times varies depending on thecharacteristics of the shut-off valve 1, the opening degree of the firsttime, and the time for which the solenoid valve 5 is turned on for ashort time after the second time, and the like.

As a result of comparison in step S313, when the allowable time isexceeded (step S314: exceeding the allowable time), the test result isheld in the memory in the microcomputer 7 (step S322) and the test iscompleted. On the other hand, as a result of comparison in step S313,when the allowable time is not exceeded (step S314: not exceeding theallowable time), the shut-off valve 1 is opened (step S315).

When step S315 is executed, the microcomputer 7 brings the solenoid Cinto a power stop state, and brings the solenoid D into an energizedstate. Then, the air from the air supply source 11 is supplied from thecommon inlet port IN of the solenoid valve 5 via the small flow ratethree-way solenoid valve 5B to the cylinder 31 from the inlet 36 via thecommon outlet port OUT. The piston 34 slides in the left direction, andthe shut-off valve 1 goes to the fully opened state.

Next, the allowable time from the predetermined opening degree to thefully opened state is read from the internal memory or the like (stepS316). The current detection value of the OUT side pressure sensor 6Band the detection value of the opening degree sensor 8 are held in theinternal memory or the like (step S317). The allowable time until fullopening is compared with (checked) the elapsed time from when theopening of the shut-off valve is started in step S215 to the presenttime (step S318).

As a result of comparison in step S318, when the allowable time isexceeded (step S319: exceeding the allowable time), the test result isheld in the memory in the microcomputer 7 (step S322) and the test iscompleted. On the other hand, as a result of comparison in step S316, ifthe allowable time is not exceeded (step S319: not exceeding theallowable time), whether the shut-off valve 1 is fully opened again ischecked (step S320).

Next, as a result of checking whether the shut-off valve 1 is fullyopened again in step S320, if not fully opened (step S321: not fullyopened), the process returns to step S317 and executes step S317 andsubsequent steps again. On the other hand, as a result of checkingwhether the shut-off valve 1 is fully opened again in step S320, when itfully opened (step S321: fully opened), the test result is held in thememory in the microcomputer 7 (step S322) to complete the test.

Therefore, step S300 functions as a set opening degree acquisitionprocess, step S305 functions as an opening degree detection process, andsteps S306 and S307 function as a control process.

According to the present embodiment, the opening degree sensor 8 fordetecting the opening degree of the shutoff valve 1 is provided, and themicrocomputer 7 controls the solenoid valve 5 to close multiple times soas to approach the set opening degree based on the detection value ofthe opening degree sensor 8. Therefore, for example, by operating finelyin the vicinity of the set opening degree, it is possible to graduallyadjust the actual opening degree to be the set opening degree.Therefore, the deviation between the set opening degree and the actualopening degree can be reduced. In addition, since it can be realizedonly by electrical control, there is no need for a mechanical mechanismsuch as extending the needle under a predetermined condition to apply abrake, and the need for additional components for testing is notrequired.

Further, the microcomputer 7 causes the shut-off valve 1 to be closedmore frequently in the first operation than the second and subsequentoperations among opening and closing the solenoid valve 5 a plurality oftimes. Therefore, the number of times of opening and closing control ofthe solenoid valve 5 can be reduced as much as possible to shorten thetest time.

Third Embodiment

Next, a shut-off valve control system according to a third embodiment ofthe present invention will be described with reference to FIGS. 12 and13. Incidentally, the same components as those in the first and secondembodiments described above are denoted by the same reference signs andthe description thereof will be omitted.

In the present embodiment, the configuration of the shut-off valvecontrol system is the same as that shown in FIGS. 1 to 4. In the presentembodiment, the delay time of the shut-off valve 1 with respect to thesolenoid valve 5 is measured preliminary instead of the coefficient Cpreliminary calculated in the first embodiment, and the open/closecontrol is performed based on the measurement result.

In the shut-off valve control device 100 having the configuration shownin FIG. 4, it is determined whether the microcomputer 7 has reached theset opening degree based on the detection result of the opening sensor8. However, as described above, since the shut-off valve 1 has a slowerreaction speed than the solenoid valve 5, even when the solenoid valve 5is closed (all port block), a delay time occurs until the shut-off valve1 is actually stopped. Therefore, in the present embodiment, the time toreach the set opening degree and the above-mentioned delay time aremeasured preliminary, and the solenoid valve 5 is closed in the timeobtained by subtracting the delay time from the time to reach themeasured set opening degree (see FIG. 12). A flowchart (time acquisitionprocess) for measuring the delay time in the present embodiment is shownin FIG. 13. The flowchart shown in FIG. 13 is executed by themicrocomputer 7.

First, as an initial setting, the solenoid valve 5 is operated to causethe microcomputer 7 to recognize the detection values of the openingdegree sensor 8 when the shut-off valve 1 is fully opened and fullyclosed (step S401). Next, PVST is executed by the operation shown inFIG. 5 (step S402). It is preferable to perform this PVST a plurality oftimes by changing the set opening degrees, such as 80%, 60%, 40%, and20%. Next, the time and delay time to reach the set opening degree aremeasured in the PVST executed in step S402 (step S403). That is, themicrocomputer 7 functions as time acquisition means for acquiring theset opening degree of the shut-off valve 1 and the time when theshut-off valve 1 reaches the set opening degree.

Note that the PVST is executed at a plurality of set opening degrees instep S402 because the relationship between the time difference and theopening degree does not become proportional due to the difference inpressure applied to the cylinder 31 depending on the opening degree.That is, the delay time is measured preliminary for a plurality ofopening degrees of the shut-off valve 1.

Then, when executing the flowchart of FIG. 5, when checking whether ornot the set opening degree has been reached in step S106, whether or notthe time obtained by subtracting the delay time from the time to reachthe above-described measured set opening degree has elapsed is checked.That is, based on the delay time of the shut-off valve 1 with respect tothe solenoid valve 5 (electromagnetic valve) measured preliminary, themicrocomputer 7 operates the solenoid valve 5 (electromagnetic valve)until the time obtained by subtracting the delay time from the time whenthe shut-off valve 1 reaches the set opening degree. That is, steps S106and S107 function as a control process.

Incidentally, it is practically difficult to measure the time to reachthe setting opening degree and delay time measured preliminary with afine opening degree such as every 1%. Therefore, as described above,measurement is made at every 20% or 10% opening degree, and when settingthe opening degree between them, it may be estimated based on thearrival time or delay time close to the opening degree to be set. Forexample, in the case where the set opening degree is 25%, when the above80%, 60%, 40%, and 20% are already calculated, estimation is performedbased on the value of 20%.

According to the present embodiment, based on the delay time of theshut-off valve 1 with respect to the solenoid valve 5 measuredpreliminary, the microcomputer 7 controls the solenoid valve 5 to openuntil the time obtained by subtracting the delay time from the time whenthe shut-off valve 1 reaches the set opening degree. Thus, themicrocomputer 7 can control in consideration of the delay of theoperation of the shut-off valve 1. Therefore, the deviation between theset opening degree and the actual opening degree can be reduced. Inaddition, since it can be realized only by electrical control, there isno need for a mechanical mechanism such as extending the needle under apredetermined condition to apply a brake, and the need for additionalcomponents for testing is not required.

Moreover, since this time difference is measured preliminary for aplurality of opening degrees of the shut-off valve 1, it is possible tocontrol with an appropriate delay time in response to the change in theoperating speed of the shut-off valve 1 depending on the opening degreedue to the pressure in the cylinder 31.

Fourth Embodiment

Next, a shut-off valve control system according to a fourth embodimentof the present invention will be described with reference to FIGS. 14 to17. Incidentally, the same components as those in the first to thirdembodiments described above are denoted by the same reference signs, andthe description thereof will be omitted.

The principal part block diagram of the shut-off valve control systemaccording to the present embodiment is shown in FIG. 14. In the presentembodiment, as shown in FIG. 14, a speed controller 40 as adjustingmeans is provided between the outlet port OUT of the solenoid valve 5and the air inlet 36 of the air cylinder 3.

The speed controller 40 regulates the flow rate of air between thesolenoid valve 5 and the air cylinder 3. The configuration of the speedcontroller 40 is shown in FIG. 15. Note that the speed controller is notlimited to the configuration and the shape illustrated in FIG. 15 andthe like, as long as it can adjust the air flow rate.

The speed controller 40 includes a substantially cylindrical main bodyportion 41 and an adjustment portion 45 inserted into the main bodyportion from one end of the main body portion 41. The main body portion41 is provided with a first connection portion 41 a protruding from aside surface portion of the cylinder and a second connection portion 41b formed at the other end portion of the main body portion 41. Thesecond connection portion 41 b is thinner than the cylindrical portionof the main body portion 41.

The first connection portion 41 a is formed with a vent 42 through whichair flows in or out from the outside. The second connection portion 41 bis formed with a vent 43 through which air flows in or out from theoutside. The vents 42 and the vents 43 communicate with an insertionhole 44 formed in the main body portion 41 so that air can be sucked anddischarged between the vents 42 and the vents 43. In the insertion hole44, a step portion 44 a is formed in the vicinity of a connectingportion with the vent 42 at the vent 43 side, and a diameter of theinsertion hole 44 is reduced. Further, a screw portion 44 b is formed onone end side of the insertion hole 44, and is engaged with a screwportion 45 b of the adjustment portion 45 described later.

The first connection portion 41 a is connected to, for example, the airinlet 36 of the air cylinder 3, and the second connection portion 41 bis connected to, for example, the outlet port OUT of the solenoid valve5.

The adjustment portion 45 includes a knob portion 45 a, the screwportion 45 b, and a restricting portion 45 c. The knob portion 45 a isformed in a substantially disk shape, and provided at one tip endportion of the screw portion 45 b exposed from the main body portion 41.The screw portion 45 b is formed in a substantially round rod shape, anda screw groove is formed between the knob portion 45 a and therestricting portion 45 c. This screw groove engages with the screwportion 44 b of the main body portion 41. The restricting portion 45 cis provided at the other end of the screw 45 b. That is, the restrictingportion 45 c is positioned in the main body portion 41 (in the insertionhole 44). Further, the restricting portion 45 c has a frusto-conicalshape which becomes thinner from the screw portion 45 b toward the tip(in the direction of the vent 43). Therefore, the restricting portion 45c can stop the flow of air into and out of the vent 43 by the slopeportion of the cone coming in contact with the step portion 44 adescribed above.

The speed controller 40 having such a configuration rotates the knob 45a of the adjustment portion 45 so as to twist the adjustment portion 45into the main body portion 41 to reduce the protrusion amount from themain body 41 as shown on the left side of FIG. 16. Then, in theinsertion hole 44, the restricting portion 45 c moves in the directionapproaching the step 44 a. Then, the distance between the restrictingportion 45 c and the step portion 44 a becomes narrowed, and the amountof air flowing from the vent 42 is restricted. Therefore, adjustment canbe made to reduce the amount of air flowing between the vents 42 and 43.

On the other hand, as shown on the right side of FIG. 16, the knob 45 aof the adjustment portion 45 is rotated to increase the protrusionamount of the adjustment unit 45 from the main body 41. Then, therestricting portion 45 c moves in the insertion hole 44 in a directionaway from the step portion 44 a. Then, the distance between therestricting portion 45 c and the insertion hole 44 becomes wide, and theamount of air flowing in from the air vent 42 increases. Therefore,adjustment can be made to increase the amount of air flowing between thevents 42 and 43.

Thus, the speed controller 40 can adjust the amount of air flowingbetween the vent 42 and the vent 43 by rotating the knob 45 a of theadjustment portion 45. The adjusting portion 45 is engaged with the mainbody portion 41 (the screw portion 44 b) by the screw portion 45 b, sothat the position of the regulating portion 45 c can be fixed at anyposition.

In the present embodiment, the speed controller 40 configured asdescribed above is provided between the outlet port OUT of the solenoidvalve 5 and the air inlet 36 of the air cylinder 3, so that the amountof air discharged from the air cylinder 3 can be reduced and theoperating speed of the cylinder 31 is restricted.

FIG. 17 shows a flowchart of an operation (a test method of the shut-offvalve control system) at the time of operation test (PVST) at the timeof setting including prediction of failure according to the presentembodiment. Steps S501 and S502 are added to the flowchart shown in FIG.17 before the flowchart shown in FIG. 5.

In step S501, the speed controller 40 is adjusted. For example, theamount of air exhausted from the air cylinder 3 is narrowed by the speedcontroller 40 to reduce the amount of exhaust air. Next, in step S502,the set opening degree is set, and thereafter, the flowchart proceeds asdescribed in FIG. 5.

That is, step S501 is an adjustment process, step S502 is an openingdegree setting process, and steps S101 to S117 are operation testprocesses.

Incidentally, in order to adjust the speed controller 40 a plurality oftimes, the flowchart shown in FIG. 17 may be executed a plurality oftimes.

According to the present embodiment, the speed controller 40 foradjusting the flow rate of air is provided between the solenoid valve 5and the air cylinder 3. Therefore, by throttling the amount of airdischarged from the air cylinder 3 by the speed controller 40, theexhaust amount is controlled. Therefore, the operating speed of thecylinder 31 is limited, and the delay of the shut-off valve 1 isreduced. Therefore, the deviation between the set opening degree and theactual opening degree at the time of PVST execution can be reduced.

Note that the fourth embodiment described above can be combined with thefirst to third embodiments. When combined with the first embodiment, thespeed controller 40 is provided between the solenoid valve 5 and the aircylinder 3, and the set opening degree is further changed by thecoefficient C. For example, since the opening and closing of the smalldiameter shut-off valve is very fast, in the case of the small diameter,the switching control at the set opening degree may not be successfullyperformed with only the coefficient C. Therefore, by attaching the speedcontroller 40, the PVST can be performed with high accuracy by adjustingthe open/close speed.

Next, in combination with the second embodiment, the speed controller 40is provided between the solenoid valve 5 and the air cylinder 3, andfurthermore, the opening and closing operation of the solenoid valve 5is performed a plurality of times to gradually approach the set openingdegree. In this case also, in the small diameter shut-off valve, theopening/closing speed is adjusted by the speed controller 40 so thatPVST can be performed with high accuracy.

Then, in combination with the third embodiment, the speed controller 40is provided between the solenoid valve 5 and the air cylinder 3 andfurther the solenoid valve 5 is controlled based on the measured delaytime. In this case also, in the small diameter shut-off valve, the PVSTcan be performed with high accuracy by controlling the solenoid valve 5based on the time when the opening/closing speed is adjusted by thespeed controller 40.

Further, the above-described embodiments only show typical forms of thepresent invention, and the present invention is not limited to theseembodiments. That is, those skilled in the art can carry out variousmodifications without departing from the gist of the present inventionin accordance with conventionally known findings. As long as theconfiguration of the shut-off valve control device of the presentinvention is provided even after such a modification, it is of courseincluded in the scope of the present invention.

REFERENCE SIGNS LIST

-   1 Shut-off valve-   1 b Valve shaft-   3 Air cylinder-   5 Solenoid valve (electromagnetic valve)-   7 Micro controller (control means, set opening degree acquisition    means, time acquisition means)-   8 Opening degree sensor (opening degree detection means)-   11 Air supply source-   31 Cylinder-   40 Speed controller-   100 Shut-off valve control device

The invention claimed is:
 1. A shut-off valve control device providedwith control means for controlling an electromagnetic valve thatsupplies and exhausts air from an air supply source to a cylinder of anair cylinder that controls a valve shaft of a shut-off valve,comprising: set opening degree acquisition means for acquiring a setopening degree of the shut-off valve; and opening degree detecting meansfor detecting an opening degree of the shut-off valve, wherein thecontrol means operates the electromagnetic valve until the openingdegree detected by the opening degree detection means becomes a valueobtained by dividing the set opening degree by a predeterminedcoefficient.
 2. The shut-off valve control device as claimed in claim 1,wherein the coefficient is calculated based on a deviation between anactual opening degree of the shut-off valve and the set opening degree.3. A shut-off valve control system provided with a shut-off valve, anair cylinder for controlling rotation of a valve shaft of the shut-offvalve, and an electromagnetic valve for supplying and exhausting airfrom an air supply source to a cylinder of the air cylinder, comprising:a shut-off valve control device as claimed in claim
 2. 4. The shut-offvalve control system as claimed in claim 3, wherein adjustment means foradjusting a flow rate of the air is provided between the electromagneticvalve and the air cylinder.
 5. A shut-off valve control system providedwith a shut-off valve, an air cylinder for controlling rotation of avalve shaft of the shut-off valve, and an electromagnetic valve forsupplying and exhausting air from an air supply source to a cylinder ofthe air cylinder, comprising: a shut-off valve control device as claimedin claim
 1. 6. The shut-off valve control system as claimed in claim 5,wherein adjustment means for adjusting a flow rate of the air isprovided between the electromagnetic valve and the air cylinder.
 7. Ashut-off valve control coefficient calculation method of calculating acoefficient by controlling means for controlling an electromagneticvalve that supplies and exhausts air from an air supply source to acylinder of an air cylinder that controls a valve shaft of the shut-offvalve, comprising the steps of: a preliminary operation step foroperating the shut-off valve to a predetermined set opening degree; anactual opening degree detection step for detecting an actual openingdegree of the shut-off valve in the preliminary operation step; adeviation calculation step for calculating a deviation of the setopening degree and the actual opening degree; and a coefficientcalculation step for calculating the coefficient based on the deviationcalculated in the deviation calculation step.
 8. The shut-off valvecontrol coefficient calculation method as claimed in claim 7, whereinthe preliminary operation step is performed for each of a plurality ofset opening degrees.
 9. The shut-off valve control coefficientcalculation method as claimed in claim 8, wherein the preliminaryoperation step operates the shut-off valve to the set opening degree aplurality of times per one set opening degree.
 10. The shut-off valvecontrol coefficient calculation method as claimed in claim 7, whereinthe preliminary operation step operates the shut-off valve to the setopening degree a plurality of times per one set opening degree.
 11. Ashut-off valve control method of a shut-off valve control deviceprovided with a control device for controlling an electromagnetic valvefor supplying and exhausting air from an air supply source to a cylinderof an air cylinder for controlling a valve shaft of a shut-off valve,comprising the steps of: a set opening degree acquisition step foracquiring a set opening degree of the shut-off valve; an opening degreedetection step for detecting an opening degree of the shut-off valve;and a control step for operating the electromagnetic valve until theopening degree detected in the opening degree detection step becomes avalue obtained by dividing the set opening degree by a predeterminedcoefficient.